This application claims a priority based on German patent application 199 27 152.6, filed Jun. 15, 1999, and the contents of that application are incorporated herein by reference.
This invention relates to a position sensor for a motor vehicle which generates, as a sensor signal, a pulse-width modulated signal that varies as a function of position.
A purpose of this invention is to provide a position sensor that measures over a wide angle or path range with a particularly high resolution. High-resolution measurement converters, for example analog-digital converters, can be used to encode sensor signals over a large position range with great accuracy. However, conceptually such converters are rather uncommon in the motor vehicle area and necessitate a relatively high degree of application effort, especially in adaptation to the sensors. Moreover they are comparatively expensive.
Another approach is to subdivide a total measuring range into several similar measuring ranges. To achieve the required high accuracy it is absolutely necessary to have error-free transition from one measuring range to the next.
With analog signal generation this is practically impossible, because even a small jitter at a transition border can lead to unacceptable errors. A conventional position sensor which generates a position-dependent-variable, pulse-width-modulated signal as a sensor signal (also abbreviated as PWM signal below) are similarly unsuitable, since they do not permit a signal range from 0% to 100%.
It is therefore an object of this invention to provide a position sensor that is capable of error-free transition between sequentially-adjacent measuring ranges.
According to principles of this invention, a total measuring range of a position sensor is subdivided into multiple sequentially-adjacent similar measuring sections, or sub-ranges, and the position sensor adds a fixed offset value to a digitalized measured value, such that a sum of a minimum possible measured value and the offset value corresponds to a pulse-width modulated signal with a minimum percentage modulation that is greater than 0%, and a sum of a maximum possible measured value and the offset value corresponds to a pulse-width modulated signal with a maximum percentage modulation that is less than 100%.